IT201700014665A1 - Heating station for semi-finished thermoplastic slabs for thermoforming lines. - Google Patents

Description

Heating station for thermoplastic sheet semi-finished products for thermoforming lines.

DESCRIPTION

The present invention relates to a station for heating thermoplastic sheet-shaped semi-finished products particularly for rotary thermoforming lines and continuous packaging lines of the FFS (form-fill-seal) type.

Known solutions are based on linear machines, such as the one described in US6094890. However, these solutions have a series of limitations linked precisely to the on-line arrangement. These limits include, for example, a very low flexibility due to the fact that the machine pitch is linked to the diameter of the containers, so that, when it becomes necessary to modify the latter, the machine must be subjected to major modifications, which mainly affect the overall length of the machine, with the consequence that a machine designed to operate on containers with a certain diameter cannot operate on containers with a larger diameter, if not at the expense of completely uneconomical adaptations or incompatible with the space originally used for the machine.

It is known from US patent 3,964,237 to produce a thermoforming line in which, to obtain thermoformed containers, semi-finished thermoplastic sheet-like products are used, in particular disks, which are individually heated, printed, filled and closed without resorting to punching.

The advantage of the known solution from US 3,964,237 is that, unlike the other known solutions which provide for the molding of a plurality of containers on a sheet of thermoplastic material fed by a reel, the volume occupied by this reel is considerably greater than that which is occupied from the sheet-like semi-finished products of US patent 3,964,237 to obtain the same number of containers.

A drawback of the known solution from US 3,964,237 is that it operates at reduced speeds. In particular, the heating station of US patent 3,964,237 works intermittently.

The object of the present invention is to provide a heating station for thermoforming lines of thermoplastic sheet-shaped semi-finished products from which respective containers are to be obtained which is capable of improving the known technique in one or more of the aspects indicated above.

Within this aim, an object of the invention is to prepare the thermoplastic sheet semi-finished products for subsequent individual thermoforming at a higher production rate than that of the known art.

Another object of the invention is to allow the continuous heating and release of semi-finished thermoplastic sheet-like products to allow their individual thermoforming.

A further object is to facilitate the handling of the thermoplastic sheet-shaped semi-finished products after their heating.

Another object of the invention is to provide a station for heating thermoplastic sheet-shaped semi-finished products and a related process which can be used in a packaging line of the FFS (form-fill-seal) type.

Furthermore, the present invention aims to overcome the drawbacks of the known art in an alternative way to any existing solutions.

Not least object of the invention is to provide a heating station which is highly reliable, relatively easy to manufacture and at competitive costs.

This task, as well as these and other purposes which will appear better later, are achieved by a heating station for thermoplastic sheet semi-finished products for a thermoforming line, characterized in that it comprises a rotating heating carousel with continuous motion around a central axis and having a plurality of heating heads radially spaced from said central axis, each heating head being suitable for receiving at least one respective thermoplastic sheet-like semi-finished product in correspondence with a first peripheral zone external to the carousel, to retain said at least one semi-finished product during rotation of the carousel while supplying it with heat, and to delivering said at least one semi-finished product to a second peripheral area external to the carousel which is angularly spaced from the first area.

The aim and objects of the invention are also achieved by a continuous heating process of thermoplastic sheet semi-finished products for subsequent thermoforming, characterized in that it comprises the steps of:

- continuous rotation of a carousel around a central axis, said carousel having a plurality of heating heads radially spaced from said central axis;

- in correspondence with a first peripheral zone external to said carousel, feeding said heating heads of thermoplastic sheet-like semi-finished products, so that each heating head passing through said first zone receives a respective sheet-like semi-finished product;

- during said rotation, holding said semi-finished products in the respective heating heads and applying heat to said semi-finished products;

- releasing said sheet-like semi-finished products to a second zone around the carousel which is angularly spaced from the first zone.

Further characteristics and advantages of the invention will become clearer from the description of a preferred but not exclusive embodiment of the heating station according to the invention, illustrated, by way of non-limiting example, in the accompanying drawings, in which:

Figure 1 is a plan view of a thermoforming and packaging line of the FFS (form-fill-seal) type using the heating station according to the invention;

Figure 2 is a perspective view of the heating carousel used in the line of Figure 1;

Figure 3 is a perspective view in axial section of a heating head of the carousel of Figure 2, in the open configuration;

Figure 4 is a perspective view in axial section of a heating head of the carousel of Figure 2, in the clamping and heating configuration of the semi-finished product;

figure 5 is a side elevation and sectional view of a heating head of the carousel of figure 2, in the configuration of clamping only of the semi-finished product;

Figure 6 is a diagram of the articulated quadrilateral mechanism used in the heating head of the previous figures.

With reference to the aforementioned figures, a packaging line for the thermoforming of containers that can be filled with bulk material, indicated globally with the reference number 1, comprises a warehouse 2 of thermoplastic sheet-like semi-finished products G, a station 3 for feeding the semi-finished products to a subsequent heating station 4 of the semi-finished products, a thermoforming station 5 of containers starting from said semi-finished products, a station 6 for filling containers with the bulk material, a sealing station 7 for containers filled with seals fed by a station for feeding the seals 9.

The semi-finished thermoplastic sheet-like products G comprise, or consist entirely of, a "token" made of a tem-formable plastic material, for example a thermoplastic polymer, preferably of the type suitable for food, such as PS, HIPS, PET or the like. In general, each semi-finished product G can have any shape in plan, for example round, square, rectangular, oval, polygonal, corresponding to the plan of the final container to be made or of the edge of its mouth. In the preferred and illustrated embodiment, each semi-finished product G is suitable for forming a single container and has, but is not limited to, a discoidal shape.

Preferably, the containers obtainable with the thermoforming station 5 are jars, suitable for example to be filled in the filling station 6 with an edible substance in the form of particulate or fluid, for example with yogurt, to then be sealed with tear-off foil lids. or "peelable" (eg plastic / aluminum laminates).

The heating station 4 comprises a heating carousel 41 rotatable with continuous motion around a central axis H and having a plurality of heating heads 42 radially spaced from said central axis H.

Each heating head 42 is suitable for receiving at least one respective thermoplastic sheet-like semi-finished product G in correspondence with a first peripheral area 43 external to the carousel, to retain said respective semi-finished product G, preferably by axial clamping, during the rotation of the carousel while supplying it with heat. to make it reach a thermoforming or permanent deformation temperature, and to release the semi-finished product thus heated to a second peripheral zone 44 external to the carousel 41 and angularly spaced from the first zone 43. An output star 81 can be provided in the second peripheral zone 44, which constitutes the inlet star for the subsequent thermoforming station 5 and which transfers the heated semi-finished product G from station 4 to station 5.

Each heating head 42 can comprise clamping means 420 suitable for retaining the semi-finished product G on a clamping plane P at the periphery of the semi-finished product G during its heating. Each heating head 42 can also comprise at least one heat source 450 which is associated with the clamping means 420 and which is movable with respect to the clamping plane P so as to heat an area of said semi-finished product not affected by said clamping. For example, when the semi-finished product G has a disc shape, as in the case illustrated in the drawings, the area 449 of said disc which is heated up to at least the thermoforming temperature of the material of the semi-finished product G is a circle with a diameter smaller than that of the disc, thus leaving on the disc a "cold" circular ring 423 on which the clamping means 420 act to hold the disc during the rotation of the carousel 41 until it is released to the output star 81.

The clamping means 420 preferably comprise at least two jaws 421-422 axially opposed and mutually movable along a clamping axis C substantially parallel to the central axis H of rotation of the carousel 41 to clamp the blank G between them at its periphery 423 .

These jaws 421, 422 can comprise respective annular structures 424, 425 provided with respective protrusions 426, 427, for example arched walls, which clamp the periphery 423 of the semi-finished product G on opposite faces. The annular structure 424, 425 is preferably made at least partly in thermally insulating material and possibly the projections 426, 427 are perforated so as to reduce as much as possible the heat exchange with the periphery 423 of the semi-finished product G.

The jaws 421, 422 are preferably mounted slidingly on the same rectilinear guide 430 fixed, directly or indirectly, on the periphery 410 of the heating carousel 41 and directed parallel to the clamping axis C.

For example, in the preferred embodiment illustrated, the annular structures 424, 425 are mounted on annular supports 428, 429 cantilevered on sliders 431, 432 slidably fitted on the rectilinear guide 430. This guide 430 can be fixed to brackets 433, 434 of a rod 435 fixed directly on the periphery 410 of the heating carousel 41.

The jaws 421, 422 can also be connected to an articulated quadrilateral mechanism 440 associated with a follower 441 which interacts with a fixed cam 442 of the heating station arranged in a fixed position around the axis of rotation H, so as to bring or reciprocally moving the jaws 421, 422 away through said articulated quadrilateral.

The articulated quadrilateral mechanism 440 may comprise a rocker arm 443 having a fulcrum F rotatably mounted on a fixed point of the periphery 410 of the heating carousel, for example on the rod 435, and having the two respective ends 444, 445 connected to a respective jaw 421, 422 by respective connecting rods 446, 447, so that a rotation of the rocker arm 443 around the fulcrum F entails the reciprocal approaching or distancing of said jaws 421, 422.

The connecting rods 446 and 447 can be hinged on the respective sliders 431, 432.

To control the rotation of the rocker 443, one of the ends of the rocker 443, for example the first end 445, is advantageously connected to the follower 441, which is preferably of the rocker arm and roller type, so that the interaction between follower 441 and cam fixed 442 controls the rotation of the rocker and consequently the opening and closing of the jaws 421, 422. The connection between follower 441 and the end 445 of the rocker in this case is obtained by means of a third connecting rod 448.

In an alternative embodiment, not shown, a cam follower roller can be applied directly to the aforementioned end 445 of the rocker arm.

The heat source 450 is also movable along the clamping axis C, and is moved in particular by means of an actuation independent of the one which reciprocally moves the two jaws 421, 422, for example by means of a pneumatic actuation.

The heat source 450 is preferably of the resistive type and can be mounted on a pair of supports 451, 452 which can be approached each other on opposite sides towards the clamping plane P, preferably in such a way as to grip both faces of the semi-finished product G and transmit the heat by conduction on a limited area 449 of these faces destined to be deformed during the subsequent thermoforming.

For this purpose, the supports 451, 452 of the heat source comprise a surface 453, 454 for transmitting heat by conduction having an extension smaller than the area of the faces of the blank G to be heated, so that the clamping operated by the jaws 421, 422 takes place in a peripheral sector 423 of the semi-finished product which is not directly heated by the heat source 450.

In an alternative embodiment, not shown, the heat transmission can take place by irradiation, for example in the case of a heat source of the IR lamp type. In this case, the divergence of the IR beam will be such as to heat only the area 449 to a thermoforming temperature.

The operation of the heating station is evident from what has been described above. In particular, a continuous rotation of the carousel 41 is carried out around the central axis H, for example by means of a motor in direct drive on the central shaft of the carousel or connected to this shaft by means of a transmission. In Figure 1, the direction of rotation of the carousel 41 is counterclockwise.

The fixed cam 442 can be configured in such a way as to make the rocker 443 rotate in the direction of the mutual distancing of the jaws 421, 422 in correspondence with the feeding station 3 and in particular in correspondence with the second external peripheral zone 44, so that each head 42 receives a respective sheet blank G from the feeding station without stopping. The rotation of the rocker arm in the opening direction of the jaws can alternatively be operated by means of a spring, not shown, which acts on the follower 441 or directly on one end 444, 445 of the rocker 443.

After the insertion of the semi-finished product G between the clamping means 420, for example by releasing the semi-finished product G resting on the projections 426, a rotation of the rocker arm 443 is performed in the opposite direction to that of the opening of the jaws 421, 422, through the interaction between the followers 441 and the fixed cam 442, thus retaining the semi-finished products G in the respective heating heads 42 along the path from the first zone 43 towards the second zone 44.

During this path, the reciprocal approach of the supports 451, 452 of the heat source is pneumatically controlled so as to heat the area 449 of the semi-finished product G. The temperature reached is substantially equal to or higher than that of thermoforming or permanent deformation of the material. which constitutes the semi-finished G.

Once the second peripheral zone 44 has been reached, a new rotation of the rocker 443 is carried out to allow the release of the semi-finished products G, for example to the output star 81.

In practice it has been found that the invention achieves the intended aim and objects by achieving it

The invention, thus conceived, is susceptible of numerous modifications and variations, all of which are within the scope of the inventive concept; moreover, all the details can be replaced by other technically equivalent elements.

In practice, the materials used, as long as they are compatible with the specific use, as well as the contingent shapes and sizes, may be any depending on the needs and the state of the art.

Where the features and techniques mentioned in any claim are followed by reference marks, these marks have been affixed for the sole purpose of increasing the intelligibility of the claims and consequently such reference marks have no limiting effect on the interpretation of each element. identified by way of example by these reference signs.

Claims (9)

CLAIMS 1. Heating station (4) for thermoplastic sheet semi-finished products for a thermoforming line (1), characterized in that it comprises a heating carousel (41) which rotates continuously around a central axis (H) and has a plurality of heating heads (42) radially spaced from said central axis, each heating head being suitable for receiving at least one respective thermoplastic sheet-like semi-finished product (G) in correspondence with a first peripheral area (43) external to the carousel (41), to retain said at least one semi-finished product (G) during the rotation of the carousel (41) while supplying it with heat, and to release said at least one semi-finished product (G) to a second peripheral area (44) external to the carousel which is angularly spaced from the first area (43). Heating station according to claim 1, wherein each heating head (42) comprises: clamping means (420) suitable for holding said at least one semi-finished product on a clamping plane (P) at the periphery (423) of said semi-finished product (G) during its heating; and at least one heat source (450), which is associated with said clamping means (420) and which is movable with respect to said clamping plane so as to heat an area (449) of said semi-finished product not affected by said clamping. 3. Heating station according to the preceding claim, wherein said clamping means (420) comprise at least two jaws (421, 422) mutually movable along an axis (C) substantially parallel to the central axis (H) of rotation of the carousel for clamping said at least one semi-finished product (G) between them at the periphery (423). 4. Heating station according to the preceding claim, in which said jaws (421, 422) are mounted slidingly on the same straight guide (430) fixed on the periphery of the heating carousel (41) and are connected to an articulated quadrilateral mechanism (440) associated with a follower (441), said heating station (4) further comprising a fixed cam (442) adapted to interact with said follower (441) so as to reciprocally approach or move away said jaws through said articulated quadrilateral (440). Heating station according to the preceding claim, wherein said articulated quadrilateral mechanism (440) comprises a rocker arm (443) having a fulcrum (F) rotatably mounted on a fixed point of the periphery of the heating carousel and having two ends (445 , 444) of which one (445) is associated with said follower (441), said jaws (421, 422) being connected by respective connecting rods (446, 447) to a respective end of said rocker arm (443) so that a rotation of said rocker arm due to the interaction of said follower (441) with said fixed cam (442) involves the reciprocal approaching or moving away of said jaws. 6. Heating station according to one or more of claims 3-5, wherein said heat source (450) is movable along said axis (C) substantially parallel to the central axis (H) through a drive independent of that (440) which reciprocally moves said at least two jaws, preferably through a pneumatic drive. 7. Heating station according to the preceding claim, wherein said heat source (450) is mounted on a pair of supports which can be approached each other on opposite sides towards said clamping plane (P). 8. Heating station according to the preceding claim, wherein said supports of the heat source comprise a heat-transmitting surface having a surface extension smaller than the area of the face of said at least one semi-finished product to be heated, so that the clamping operated by said jaws has located in a peripheral sector of the semi-finished product which is not heated by said heat source. 9. Continuous heating process of thermoplastic sheet semi-finished products for subsequent thermoforming, characterized in that it comprises the steps of: - continuous rotation of a carousel (41) around a central axis (H), said carousel having a plurality of heating heads (42) radially spaced from said central axis; - in correspondence with a first peripheral zone (43) external to said carousel, feeding to said heating heads of semi-finished thermoplastic sheet molds, so that each heating head passing through said first zone receives a respective plate-like semi-finished product; - during said rotation, holding said semi-finished products in the respective heating heads and applying heat to said semi-finished products; - releasing said sheet-like semi-finished products to a second zone (44) around the carousel which is angularly spaced from the first zone (43).